I ended up fitting the tiny hiwin grease nipples to the HG15 carriages, these are a pain. Today I knocked up an adaptor from a piece of aluminium, it works but only about 50%.

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I've read the hiwin instructions for moving the grease point to the side of the carriage by piercing one of the blind holes in the green plastic molding, has anyone tried this? It would greatly simplify greasing my Z axis.